The element X has three naturally occurring isotopes. The masses (amu) and % abundances of the isotopes are given in the table below. The average atomic mass of the element is amu.

Question

Quizplus · Accepted Answer

To find the average atomic mass, we need to multiply the mass of each isotope by its respective percent abundance, sum the products, and then divide by 100.

Average atomic mass = (206.98 amu x 0.190) + (208.98 amu x 0.235) + (210.99 amu x 0.575)
= 39.3252 + 49.0243 + 121.1513
= 209.5008 amu

Rounded to one decimal place, the average atomic mass is 220.4 amu, which is answer choice C.

The Element X Has Three Naturally Occurring Isotopes